Lens



E. D. TILLYER.

LENS.

APFLICATlON FlLED NOV. 29. 1916.

Patente Feb. 14, 1922..

Prior 14 ff/ PNT orFlcE.

EDGAR D. TILLYER, OF SOU'I'I'IBRIDGE, MASSACHUETS, ASSIGN'OR. T0 AMERICAN GPTICAL CGMPANY, OF SUTHBRIDGE, MASSACH'USETTS, A VQLUNTARY ASSO- CIATION GF MASSACHUSEK'TS.

LENS.

Specifieation of Letters Patent.

ratentea nen, 14, ieee.

Application filed tovcmber 29, 1916. serial No. 134,129.

T0 all 'whom it may conccrn:

Be it6 known that I, EDGAR D. Tinnrnn, a citizen of the United States, residing at Southbridge, in the county of lworcester and VState of Massachusetts, have invented certain new and useful Improvements in Lenses, of which the following is a specification.

|This invention relatos to improvements in lenses and has particular reference to that form of lenses commonly known. as double lvision or bifocal lenses.

with Ordinary forms o-f bifocal lenses when E All the eye passes from one to the other oi me visual portions of the lens.

A further object of the present invention is the provision of a novel and improved form of lens which will to a large degree eliminate the objectionable prismatic difficulties present in connection with ordinary bifocals and which will do away with the dangers present with previously employed bifocals having a prism base down, causing the object seen through the bifocal portion to appear higher than it actually was by substituting the bifocal portion having its prism for normal correction base up, by which the efiect is produced of the object being slightly lower than is actually the fact,

so that a person looking through the bifocal portion at a flight of steps or the like which they are about to descend, shall appreciate the full distance down tothe steps being looked at through the bifocal portion rather than under-estimating the distance, as is liable to occur with present types of bifocals.

A further object of the present invention is the provision of a one-piece lenswhich shall satisfactorily attain all of the foregoing results and at the same time ie capable of manufacture in an extremely light and desirable form.

Other objects and advantages of my improved construction should be readily apparent by reference to the following specification taken in connection with the accompanying Idrawings forming a part thereof, and it will be understood that I may make any modificationsiin the specific details of construction shown and described Within the scope of the appended claims without departing from or exceeding the spirit of my invention.

Figure I represents a front view of a mounting equipped with a pair of my improved lenses.

Figure H represents a view of a present known type of lens illustrating the displacement occasioned by the double centers and prism in the reading portion.

Figure III represents a semi-diagrammatic Sectional view of this form of lens illustrating why the displacement of objects occur.

Figure IV represents a view similar to Figure If illustrating the principle of my improved lens.

Figure V represents a view similar to Figure III showing how the desired result is accomplished.

Figure VI represents a detailed view illustrating the method of laying out the previously employed forms of bifocals.

Figure VII represents a similar view illustrating the laying out of my improved bifocal.

Figure VIII represents a semi-Sectional perspective view showing the structural appearance of my improved lens.

Figure IX represents a view of a prior art form of concave bifocal.

Figure X is a similar view of one of my\ improved bifocals giving the same prescriptive value.

In the drawings, in which similar characters of reference are employed to denote corresponding portions of the lenses illustrated throughout the several views, the numeral 1 denotes the anterior curve of a lens the numeral 2, the ocular curve of the D. or distance portion, and the numeral 3, the ocular curve of the R. P. or reading portion, these threecurves being customary curves present in all bifocal lenses, and their relationship producing the two desired powers in the lens.

As particularly illustrated in Figures II, III, VI and IX, of the drawing showing the prior art, it has been customary hitherto in the production of bifocal lenses, to so calculate and grind the foregoing curves with respect to each other that the distance portion of the lens as an entirety will have its center disposed substantially at 4, while the reading portion will have its center disposed substancri tially at the point 5. By center of the lens it is understood to mean the meridian of the lens at which a straight line or other image viewed through the lens will present a continuous line through the lens and at the points outside the lens, this being the point in other words at which there is no prismatic displacernent of the image as seen in the lens to a point either above or below its actual 'relative relation to the line of vision.

In the form illustrated in Figure II the actual position of the line 6 being considered as viewed through the lens, is at the point of joinder of the D. P. and It. P., so that were the lens centered in accordance with my improvement the line 6 would be continuous in the light line 7 indicated in Figure II. In actual practice, however, a person looking through the lens at the line of joinder 8 of the distance and reading portions will find their vision divided so that two images are produced in the eye.

Consequently the actual line being considered for test purposes, located at 6, will be seen on account of the prism present in the distance portion at the point 8, as a line in the position indicated by the dash line 9, while at the same time a shorter image, as indicated by the second dash line 10, will be seen considerably above the normal position 7 on account of the prism present in the reading portion, so that as the eye crosses the line of joinder 8 in place of the single image as 7, being noted, the double image will appear, comprising the lines 10 and 9, causing momentary confusion of the vision.

In connection with my improvement, however, the center of my lens being placed at the point 11 or on the line of joinder between the reading and distance portion, the continuous image line 12 will be noted as the eye is passing from the one focus to the other. In addition, as is noted in connection with Figure V, should the line of vision be downward through the reading portion, the point being looked upon Will be displaced downwardly in place of upwardly.

The general method of laying out an ordinary bifocal should be best understood by reference to Figure VI, in which has been illustrated the lens proper in full line and the remainder of the blank from Which the lens is formed in the dotted line, in this figure the line 13 denoting the axis on which the center 17 for the front face curve, and the center 15 for the reading curve are located. Similarly, the line 16 passes through the point 14 or center for the ocular distance vision curve and the center 17 for the anterior'curve 1 of the lens roper, this line passing through the optical center 4 of the distance portion of the lens. By reference to this figure it will thus be seen there are the two entirely distinct centers as previously referred to in connection with Figures i ,acessa I and II, and it will. further be noted, as is further brought out or accentuated in connection with the extreme lens illustrated in Figure IX, that considerable prism is added in connection with the reading portion.

In contrast with these Figures VI and IX, attention is invited to Figures VII and X, illustrating the principles of my invention, from which it will be seen that the axis or center line 18 passes through the lens atthe point' of intersection or mergence of the reading portion and distance portion and that the centers of curvature of the anterior curve 1' and the ocular curves 2 and 3 are all located on the line 18, this relationship necessitating the optical center being disposed on the line of mergence and at the same time insuring true and proper merging of the curves so that all possibility of a jump in the image in passing from the reading portion to the distance portion is eliminated and the change in position is gradual in place of sudden, while at the same time this relative positioning of the parts in connection with the eXtreme concave bifocal type illustrated in Figure X for example almost entirely eliminates prism from the lens in place of considerably increasing the thickness of the lens and the prism effect, as in 'the case with the old style form of bifocal.

I would call particular attention to the showing of my improved lens in Figure VIII, from which it will be noted that by selecting the proper position for the center of the curve 3 along the axis line the surface 3 is so adjusted that it centrally blends into or merges with the adjacent portion of the curve 2, while on account of its tilted relation the sides bordering the countersink or segment portion laterally fall below the planeof the distance curve, producing a ridge of gradually increasing height from central,

portion to edge of the lens, -as will be clearly apparent by reference to Figure VIII in question. It will thus be seen that in the central portion the two surfaces on account of regulation of their heights or positions of centers along the axial line have a merged or ridgeless portion, while the segment due to its fiatter or less co'ncave curve falls below the surface of the major portion laterally.

This lens can be produced by apparatus and processes well known to the art and to me long prior to my invention; in fact by the apparatus and processes by which the prior art bicentric onepiece bifocal lenses are and have been made. 1One expeditious method is to firsfi grind and polish, either .with the prior-art spherical lap tools, or with the prior art ring grinding and polishing tools, the distance portion on the bifocal side of the lens; then tilt the lens, a procedure well known in the prior art, on its holder to the proper angle to relate the reading portion to the distance portion, and then grind Ali fio

and polish the reading portion with the prior art lap or ring grinding and polishing tools. The side opposite the bifocal side may then be ground and polished With the Ordinary spherical, toric or cylindrical lap tools, as the case may be. The apparatus used is that used for making the prior art bicentric onepiece bifocals; namely, a revolvable lens Vholder for carrying the lens and an opposed revolvable spindle for carrying the lap or ring tools. rf`hese methods and apparatus have been used in England and in the United States to my knowledge several years before my invention.

From the foregoing description taken in connection with the accompanyingcdrawings, the construction of my improved bifocal and its numerous advantages should be readily apparent, and it will be seen that I have provided a simple, light and attractive bifocal, in Which there is no jump noticeable in the image, but in which the surfaces merge together at the central portion where the eye normally passes from the distance to reading portion or vice versa, in which the undesiri able prism effect present in most bifocals, is

eliminated, and which may be readily constructed from a single piece of glass, Vparticularly in the meniscus or toric type, by cutting away a predetermined portion of a semi-finished or finished lens having the desired anterior curve for the distance vision, although it will be understood that I may if preferred first form my reading addition curve on the major blank and subsequently grind the distance curve, the only effect being a variance in the mergence or line of joinder of the parts, accordingto the order of ILperformance of the grinding operation.

clairn:

1. A concave Convex bifocal lens formed with a convex single vision curve on the one face and with a pair of intersecting concave curves on the opposite face, the center of curvature of the weaker concave surface lying in a line determined by the centers of merging together in the vertical meridian on the opposite face thereof, the center of the three curves lying in an axis passing through the optical center of the lens at a point eccentrie to the geometrical center of the reading portion of theclens.

3. A one piecebifocal lens'having a concave distance portion curve on the bifocal side and a less concave reading ortion curve on the bifocal` side, said rea ing portion curve merging centrallyy with the distance portion curve and being downwardly tilted with respect thereto to ,introduce a prism base up effect in the reading portion.

4z. A one piece bifocalfllens of meniscus centers of curvatura of the three surfaces lying in a common axis to produce a monocentric bifocal, and the positions of the centers of the concave curves being disposed along the axis to merge the two concave curves at a point adjacent their common optical center.

6. A bifocal lens consisting of a single piece of material having the optic axis of the near field at the top edgeof said near field.

7 A lens formed of a single homogeneous piece of glass having on one side a single lenticular surface area, and on'the opposite side a plurality of lenticular surface areas, these being ground an'd'finished thereon and arranged to have a common principal axis.

8. A lens formed of a single piece of homogeneous glass finished on one side With a common or, single lenticular surface area, and molded on the other side so as to have areas of different depths, these being finished to produce distinct visual areas, and the several lens areas having a substantially common principal axis.

9. A bifocal lens, comprising a single crystal having a continuous curve on one face thereof and a pair of intersecting curves substantially merging together in the vertical meridian on the opposite faee thereof, the

centers of the three curves lying in an axis passing through the optical center of the lens at a point eccentric to the geometrical center of the reading portion of the lens.

10. A multifocal lens made of one piece of material having a plurality of distinct' spherical surface areas ofdifferent foci on' one side thereof, all of Which surfaces have a common tangent in one meridian.

11. A multifocal lens made of one piece of material having on one side thereof two distinct spherical surface areas of different foci both of Which surfaces have a common tangent in one meridian.

12. A multifocal lens made of one piece of material having a plurality of distinct spherical surface areas of different foci on one side thereof, all of Which surfaces are tangent to a plane perpendicular to a line through the centers of curvature ofsaid surfaces and passing through the point of Osculation thereof.h

13.'I A Vmultifocal lens made of one piece of material which has an optical path length within the. lens for one point of one focal area identical with the optical path length within the lens of an adjacent point in a different focal area.

14. A multifocal lens made of one piece of material having upper and lower visual areas, said lens being formed with a prism base up in the lower portion of such value that there is no optical displacement in passing from one area to the next area in one meridian.

15. A device of the character described including a transparent member of one piece of material having formed on one side thereof a plurality of spherical surface areas of p different foci, all of which surfaces have tangents normal to a line through the centers of curvature of said surfaces.

16. A one-piece multifocal lens having a plurality of surfaces of different focal value on one face, said surfaces intersecting in one meridian Without cliff or ridge and being tilted; with respect to each other a'suficicient amountto elimnate prismatic displacement at said line of joinder.

Moema 17. A bifo'cal lens made of one pieceof material having on one face thereof two spherical surface areas, the centers of which lie in a line passing through a. point on the line of separaton of the two surfaces.

18. A bifocal lens made of one piece of material having on one face thereof two spherical surface areas, the centers of which lie in a line passing through a point and on the line of' separation of the two surfaces, said centers being disposed ony the ocular side of thelens.y

19. A bifocal lens made of one piece of material having two distinct focal areas on one face thereof, which surfaces have tangents perpendicular to a line passing through the centers of curvature of the two surfaces and through the line of separaton thereof.

ln testimony Whereof I afiix my signature in the presence of two witnesses.

EDGAR D. TILLYER,

Witnesses:

EDITH M. HALvonsEN, H. K. PARsoNs. 

